The non-exhaust emissions from vehicles

During general wear and tear of a vehicle, brakes and tyres can produce tiny pieces of particulate matter, which can enter the air and sea and be harmful to human and marine life. The government is now investigating the extent of the issue and ways to resolve it. GreenFleet examines the problem

While the priority for air quality has been to address high levels in nitrogen dioxide limits, due primarily to emissions of nitrogen oxides from road traffic, the government’s attention has turned to other air pollutants.
Brakes, tyres and road wear can produce tiny pieces of particulate matter – for example dust and soot – that comes from general wear and tear.

These particles are left on our roads and when it rains can be deposited into sewers and oceans, leading to harmful consequences to marine wildlife and food chains.

These emissions can also be breathed in, contributing to respiratory illnesses. It is these emissions that are now subject to scrutiny and the government has launched a consultation to improve its understanding of the extent and impact of emissions from brake, tyre and road wear and potential ways to address them.

This was part of the commitments made in the government’s Clean Air Strategy, which stated that the government would “work with international partners to research and develop new standards for tyres and brakes to enable us to address toxic non-exhaust emissions of micro plastics from vehicles which can pollute air and water”.

Other measures in the strategy include ending the sale of new conventional petrol and diesel cars and vans by 2040; making manufacturers recall vehicles and machinery for any failures in their emissions control system; and make tampering with an emissions control system a legal offence.

The UK has targets in place to reduce emissions of five damaging air pollutants (ammonia, nitrogen oxides, non-methane volatile organic compounds, fine particulate matter and sulphur dioxide) by 2020 and again by 2030.

Evidence suggests that as emissions from exhausts decrease, particulate emissions are a cause for concern, particularly due to the potential for road traffic to increase in the future. In some cases, the particulate matter emissions from brake wear, tyre wear and road wear may be more than that from the exhaust.  

Abrasion of tyres and road paints produce micro-plastic particles, which enter rivers and lakes from road run-off and can eventually be deposited into the sea. Microplastics have well-documented impacts for marine wildlife and the food chain, and studies by the University of Plymouth estimate that emissions from tyre wear alone make-up five to ten per cent of microplastics deposited in the oceans.

The government is now gathering evidence on these non-exhaust emissions, to review estimates of their contribution to air pollution, to develop forecasts for how they will evolve in the future, identify solutions to the problem, and understand the policies that might support that work. The government wants to understand and quantify the true scale of the problem and also identify any potential abatement methods, new technologies or opportunities for innovation in this area.

Bosch Mobility Solutions, for example, has recognised the problem of brake dust and has developed the iDisc which has a hard tungsten carbide coating, which reduces brake dust and increases safety. In terms of cost, the iDisc is roughly three times more expensive than a normal cast iron brake disc, but the price is likely to continue falling as production volume increases.

The evidence gathered from the consultation will inform the government’s final Clean Air Strategy, which will be published for later this year, following the current consultation,
and also inform the marine strategy.
The evidence will also be shared with the Air Quality Expert Group, a Defra advisory body, which is reviewing these emission sources to provide advice on how to address them.

Environment Minister Thérèse Coffey said: “While we are all now well aware that fumes from the exhaust pipes on our cars can have a detrimental impact on human health, it is less well known that tiny particles that are released from our brakes and tyres also contribute to air pollution and can harm our precious marine life.

“This call for evidence will help us to learn more about how these particles are released as well the actions we can take to reduce their impact. I encourage anyone who has evidence or solutions to share to get involved.”

Transport Minister Jesse Norman said: “Particulate pollution from exhausts has been reduced substantially in recent years. But we must also take action to reduce the very serious pollution caused by the wear of tyres, brakes and roads.

“Tackling this issue is crucial for reducing air pollution. We would urge anyone who has expertise in this area to get involved and share their evidence and views.”
Professor Thompson, head of the international marine litter research unit at the University of Plymouth, said: “The types of microplastics entering the marine environment are incredibly diverse, but recent estimates in Norway and Sweden have suggested that particles of tyre and debris from the road surface could be a substantial source. With very limited real data available to confirm the impact from these sources, there is a genuine and pressing need to establish the true scale of this issue.

“We will be able to use our findings can to work with the government, scientists and industry to try to prevent these particles entering the marine environment in the future.”

Commenting on this consultation, LowCVP’s MD Andy Eastlake said: “With rapid improvements in exhaust emissions, other sources of pollution are becoming a significant focus for further emission reductions.

“A lack of clear data and robust evidence means very little is known about brake emission or tyre and road particulate impacts. The government is keen to encourage any stakeholders to contribute to the call for evidence to help inform both future research and policy direction.”

The government’s Call for Evidence will run until 28 September 2018. It is aimed at stakeholders such as industry bodies, companies, environmental groups, consumer groups, academics and others who may have evidence and experience in this area.

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